External EGR, where exhaust gases are fed back into the inlet manifold is rare or unheard-of lately in petrol engines. Tends to be done by valve overlap and adjustable valve timing now, I believe.

I think from around 2006 petrol engines started shedding external EGRs, in VW group stuff anyway.

Diesels naturally make more NOx and need more EGR (and latterly SCR/Adblue) to deal with it.

Edited 24 July, 202524 Jul by Breezy_Pete
sp, as usual

19 hours ago, Graham Butcher said:

Is EGR only applicable to diesels then?

Some petrols do have an EGR valve (my previous Toyota Aygo for example) but others have a form of EGR created by valve overlap timing.

Hello. Since I started using premium gasoline, the misfires have become less frequent, if they used to be daily, now they are about once a month

The deactivation of the 2 cylinders is annoying. There is a jerking sensation when it deactivates. Could it be related to the misfires being on cylinders 2 and 3 where the deactivation occurs?

On 02/10/2024 at 16:29, gm73 said:

Thanks for the input. Checking Google it seems to be highlighting carbon build up

on the inlet valves as the main culprit. I’ve purchased some arch oil snake oil and will see if that will make a difference. 

Possible to know what was the issue and how did you fix that?

On 21/02/2026 at 19:19, bgd1106 said:

The deactivation of the 2 cylinders is annoying. There is a jerking sensation when it deactivates. Could it be related to the misfires being on cylinders 2 and 3 where the deactivation occurs?

Ive owned 3 of these engines, never experienced any jerking sensation when 2 cylinders deactivate.

Premium fuel has never made any noticeable running difference, either. I use e10 most of the time, this engine seems to run as happy on this as using the higher octane fuel.

The only time I've ever noticed any hesitation, is occasionally from cold, which is a known issue for this engine, also when I had failing plugs.

Ive also changed my oil on a regular basis, yearly at 9k, using 0w 20 oil. Changed my plugs every 2 years, not every 4 years as stipulated by skoda.

4 years / 40,000 miles is the recommendation, guidelines, suggested schedule given by VW Group / Skoda. There is no stipulation / demand that the spark plugs are changed then. But if paying a service Plan or as was MAJOR SERVICE Costs then the Dealership should have been replacing them then. Servicing according to how VW / Skoda showed.

3 hours ago, Evolution13 said:

4 years / 40,000 miles is the recommendation, guidelines, suggested schedule given by VW Group / Skoda. There is no stipulation / demand that the spark plugs are changed then. But if paying a service Plan or as was MAJOR SERVICE Costs then the Dealership should have been replacing them then. Servicing according to how VW / Skoda showed.

Two of my plugs failed on my previous 1.5tsi Octavia within two years of them being replaced by skoda. I then managed to get skoda to replace them again under their two year parts guarantee, but they would only replace the two for free, so I paid them to replace the other two, whilst they had my car. Although they didn't charge me labour for the two I paid them to replace lol. I really didn't see the point of only replacing two at that point, as two of the original 4 they'd replaced had failed.

@Phoenixboy Which year of manufacture 1.5 TSI ACT was that one. Do you know which 2 plugs failed. Cylinders that fire all the time or the 2 that are Deactivated / Cylinder on demand? ACT / COD. Clearly some issue, engine management or A.N. Other. Did they do a Software Update as well as replacing the plugs?

missfires are serious defects detected by ecu and after certain number of them check engine light will occur.

if not, those are not missfires, maybe jerking or something, but not classic missfires. with missfires you cant pass MOT.

BTW, act i good system, when driving in city when you lift throttle pedal it engages and make lean mixture to clean GPF filter, it is not just about economy. i dont see any economy benefit because driving sporty.

Vehicles with Misfires can pass a MOT in the UK if the Emissions reading on the machine is within its limits. If not then there would be even less Mk2 Fabia vRS on UK Roads. Plenty have too high readings and a fail, but lots might not have on a Engine Management light and no Logged Fault codes, but have 'Misfires'.

i had renault 1.6 before and now karoq 1.5 , all gasoline cars and when missfires occures after that MIL light on dashboard, with that cant pass mot in my country..

1 minute ago, imart143 said:

i had renault 1.6 before and now karoq 1.5 , all gasoline cars and when missfires occures after that MIL light on dashboard, with that cant pass mot in my country..

The MIL being lit is the important part, many misfires are not consistent enough and frequent enough to set the MIL (the ECU software allows a few misfires happening infrequently) - as @Evolution13 points out provided emissions are with limits then the MOT will pass.

There is a certain amount in a cycle before fault codes for misfires are logged, or before a warning light, or even before a vehicle goes into Limp Mode, maybe even disabling the Turbo.

probably. on both cars i didnt feel nothing when driving, normal driving, just until mil occured, when i scanned errors were multiple random misfire detected and missfire detected on cylinder 1, 2, 3, and 4.

on renault wrong sparkplugs were in engine, replacing solved missfires and MIL. on tsi intake was full of carbon buildup, after cleaning, also solved..

8 hours ago, Evolution13 said:

@Phoenixboy Which year of manufacture 1.5 TSI ACT was that one. Do you know which 2 plugs failed. Cylinders that fire all the time or the 2 that are Deactivated / Cylinder on demand? ACT / COD. Clearly some issue, engine management or A.N. Other. Did they do a Software Update as well as replacing the plugs?

That was on my previous 19 plate Octavia 1.5tsi se dsg estate, I now own a 20 plate with the same engine, but its the sel spec. I think it was cylinder number 2 I had the misfires on, but when Skoda took it in for a diagnostic, they said another plug was going down, too. Not sure which.

Then they tried to charge me for the diagnostic, new plugs, until I informed them that they'd replaced them during its last service, just over a year ago lol. They then appologised, offered to replace the two faulty ones for free, as the plugs were guaranteed for two years. I then paid for the other 2 to be replaced, whilst they were on. I was expecting them to replace all 4 for free, but they said their parts guarantee would only cover the ones that were faulty. Can't get much tighter than that.

Unless they didnt change the 4 initially when they said they had, that wouldn't suprise me, either.

There was no software update performed by them, afterwards, as far as I could remember.

Once the plugs were replaced, x4, engine ran sweet, again.

My own view, I dont think the plugs were initially changed, prior to me buying the car, eventhough they'd said they were changed. So at tge point of failure they may have been at least 5 years old. The car had around 65k on the clock then with a fssh. It was on two yearly oil change intervals, ex fleet. Unlike my current car, oil has been changed yearly at around 7 or 8k from new. Which I prefer.

Edited 27 February27 Feb by Phoenixboy

On 25/02/2026 at 07:58, JB1975 said:

Possible to know what was the issue and how did you fix that?

Hi there. It's still doing it occasionally after all this time so I've just ignored it. The snake oil did quieten down the engine rattle I had which was dirty injectors.

Hello. I think i have fixed the problem. I have found that i have a missing oring... now the misfires are very rarely and i have only at the starting engine for 30 second and the running is very bad... I have checked and i have -13 for injector 2. I have used an aditiv for cleaning and now is -10, and at idle the running of engine is not smoothly.